Green’s Dictionary of Slang

1. crooked, out of place, damaged, broken.

[1837		W. Dunlap Memoirs of a Water Drinker 65: His mouth was so wide, and garnished with strong teeth, and his chin with the parts adjacent, assuming the appearance vulgarly called wapper-jaw’d].
1880		Hull Packet 25 June 3/1: She despised steady girls, and called them ’whopper-jawed’.
1899		Yorks. Gaz. 22 July 9/4: What, that long, ganglin’, whopper-jawed thing? Why, I wouldn’t marry him if he was the last man on earth.
1915		M.G. Hayden ‘Terms Of Disparagement’ in DN IV:iii 219: wapper-jawed, crooked. ‘The curtain is wapper-jawed.’ [Ibid.] whocker-jawed, whopper-jawed, womper-jawed, askew. ‘A whocker-jawed skirt.’.
1970		E. Thompson Garden of Sand (1981) 239: He was certain everyone seeing him going on home with whopper-jawed handlebars was laughing at him.
1996		Eble Campus Sl. Sept. 7: whopper-jawed – not even or level.
1997–2001		Online Sl. Dict. 🌐 whockerjawed adj 1. damaged, jammed, or out of alignment. (‘I can’t open the car door because it got whockerjawed in the accident.’). [...] whopperjawed adj 1. out of place, crooked. (‘That looks whopperjawed.’).

2. crazy.

1926

Wood & Goddard Dict. Amer. Sl.